1. Field of the Invention
The present invention relates to a breathable shoe.
2. Discussion of the Background
It is known that a shoe, in order to be comfortable, must ensure proper exchange of heat and water vapor between the microclimate inside the shoe and the external one.
This exchange of heat and water vapor, however, must not compromise in any way the impermeableness of the shoe to external humidity or water.
Currently commercially available shoes entrust this exchange of heat and water vapor substantially to the upper or to the sole.
As regards the upper, shoes which are perforated and/or provided with linings made of a breathable and waterproof material are currently commercially available.
In some models, some parts of the upper can be replaced with materials which are indeed waterproof and breathable at the same time.
In rubber soles, many solutions have been proposed in order to solve the problem of the lack of breathability which is inherent in the characteristics of the material.
One of these solutions, disclosed in Italian patent No. 1232798, consists in dividing the sole into two layers with through holes and in interposing a breathable waterproof membrane which is joined perimetrically and hermetically to the two layers.
Variations of this solution occur in subsequent patents, all of which are in any case focused on dividing the sole into two layers in order to stop external water and dirt in a region which is as close as possible to the surface that makes contact with the ground.
This entails manufacturing complications and in particular prevents the provision of particularly thin soles.
In other cases, such as for example in European patent No. 275644, the entire sole is provided with through holes and is joined at the top with an upper having a bottom surface, which is entirely made of a waterproof breathable material (film of polytetrafluoroethylene porous foam) with the interposition of a protective layer made of porous material.
This structure is adapted for shoes whose upper is not provided with the classic methods, such as the ones known as “Strobel”, “ideal welt” or “pre-assembled”.
European patent No. 103601 also discloses a sole in which delimited regions are completely crossed through their thickness by holes and in which, in an upward region, a waterproof and breathable membrane is in contact with a substrate made of soft perforated material on which the foot rests; this solution is substantially equivalent to the preceding one and makes it impossible to apply classic methods.
The sole is monolithic with the upper and the entire assembly is made of plastic and is therefore not breathable.
The regions with holes are separate from the rest and are constituted by removable disks.
Substantially the same situation is proposed by French patent No. 1228239, which discloses a shoe with a sole and an upper made of the same waterproof but non-breathable (plastic) material, provided with through holes (in both the sole and the upper) and, inside the upper, a bootie made of waterproof and breathable material.
There is also an insole inside the bootie which is made of felt or similar material.